Medical professionals are often dragging their heels on progress as a matter of course, but in this case I believe the allegation is unfounded. Chemotherapy is a very dangerous treatment. It's essentially an injection of pure poison, and often people do die from complications of cancer treatment as opposed to dying from the cancer itself. Cancer drugs are terrible. Cancer surgery is often devastating. The worst thing (though maybe somewhat of a consolation in this case) is there is no real cure.

If he was diagnosed with advanced colon cancer and pushed straight into chemo, chances are the treatment was just a palliative measure designed to give him a few more weeks with less discomfort.